1. Technical Field
The present invention relates to a piezoelectric element having an electrode and a lead wiring connected to the electrode and a method for manufacturing the same, and a liquid ejecting head and a liquid ejecting apparatus having the piezoelectric element.
2. Related Art
A piezoelectric body containing crystals typified by lead zirconate titanate (PZT) and the like has piezoelectric effects and the like, and therefore is applied to a piezoelectric element. The piezoelectric element has a pair of electrodes, the electrodes on which a lead wiring for connecting to an external drive circuit or the like is formed.
Moreover, known are an ink jet recording head as a liquid ejecting head and an ink jet recording device as a liquid ejecting apparatus, in which a piezoelectric element as a pressure generating unit is provided in a pressure generating chamber communicating with a nozzle opening that ejects ink as liquid, and ink in the pressure generating chamber is pressurized to thereby eject the ink from the nozzle opening.
The piezoelectric element adopted in the ink jet recording head has, for example, a piezoelectric layer sandwiched between a lower electrode and an upper electrode. Here, there is a problem in that the piezoelectric layer is easily broken due to the external environment, such as humidity. In order to solve the problem, a piezoelectric element is mentioned in which the lower electrode is used as an individual electrode and the upper electrode is used as a common electrode, and the piezoelectric layer is covered with the upper electrode (e.g., JP-A-2009-196329).
On the upper electrode, a lead wiring for connecting an external drive circuit or the like and the upper electrode by bonding or the like is formed. Known as the lead electrode is one having an adhesion layer and a metal layer. The lead electrode is obtained by patterning (e.g., JP-A-2009-255536).
However, in patterning the lead electrode by wet etching, when an electrical conductor constituting the upper electrode as a common electrode and an electrical conductor constituting the adhesion layer of the lead electrode are different from each other, current flows through an etching solution due to differences in the ionization tendency between the electrical conductors, so that the electrical conductors melt in the etching solution, which causes electric corrosion. In particular, when the area of the common electrode is larger than the area of the individual electrode, Pt or Ir is used for the common electrode, and Ni, Ti, Cr, or the like is used for the adhesion layer of the lead electrode, a large amount of current flows through the etching solution, resulting in further progress of the electric corrosion in the adhesion layer of the lead electrode. When electric corrosion arises in the adhesion layer, the contact area between the upper electrode and the lead electrode become narrows or the separation of the lead electrode arises, which makes it difficult to obtain a piezoelectric element that can be driven by a predetermined voltage.
Moreover, current flows also through moisture or the like adhering to the surface of the common electrode and the surface of the lead electrode, which causes electric corrosion in the adhesion layer, which makes it difficult to maintain a piezoelectric element that can be driven by a given voltage and a liquid ejecting head and a liquid ejecting apparatus having the same.
The given voltage refers to a voltage for generating the deformation amount required for driving the piezoelectric element. When the contact area between the upper electrode and the lead electrode becomes narrow or the separation of the lead electrode arises, so that the resistance between the upper electrode and the lead electrode becomes high, a voltage for generating the deformation amount required for driving the piezoelectric element cannot be applied.